Shaft guard

ABSTRACT

A shaft guard for a watercraft is disclosed. The shaft guard is located inside a jet propulsion unit and at least partially surrounds the drive shaft. The drive shaft and the engine shaft are not substantially parallel. The shaft guard is attached to the housing of the jet propulsion unit at one end and may be attached to the drive shaft at the other end allowing for free rotation of the drive shaft.

[0001] This application claims benefit to U.S. Provisional Patent Application Serial No. 60/309,523, which was filed on Aug. 3, 2001, the contents of which are incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to watercraft and more particularly to a guard for the drive shaft of a jet propulsion unit for a watercraft.

BACKGROUND OF THE INVENTION

[0003] Various types of watercraft exist, each being suited for different types of activities. For example, a pontoon-type watercraft is designed for slower speeds and general recreational use and is typically powered by an outboard engine. In contrast, sport boats and personal watercraft are designed for high speeds and superior handling and are typically powered by one or more inboard engines connected to one or more jet propulsion units.

[0004] In the typical arrangement for a jet propulsion unit, an engine output shaft extends from the engine and is rotationally coupled to a drive shaft. An impeller is attached to the drive shaft. The impeller is disposed within a tunnel, which is defined by the hull of the watercraft partially below the water line. The tunnel extends from a point forward of the rear of the watercraft to the rear, generally above the ride plate for the watercraft.

[0005] During operation, as the drive shaft rotates, the impeller draws water through the inlet disposed forward of the tunnel under the hull and discharges the water, at great speed and pressure, through a nozzle at the rear (or outlet) of the water or pump passage.

[0006] The operator controls the travel direction of the watercraft by a steering device (e.g. a steering wheel or handlebars) operatively connected to the nozzle. As the nozzle direction is changed, so too is the exit flow of water from the nozzle. Accordingly, as the nozzle direction changes, so does the travel direction of the watercraft.

[0007] A grate is typically mounted to the hull to cover the intake to the water passage. The purpose of the grate is to prevent foreign matter, such as debris and weeds, from entering the water passage. The entrance of such foreign matter into the water passage potentially may damage the impeller and/or impede the performance of the watercraft.

[0008] Specifically, if weeds enter the water passage, potentially they can wrap around the drive shaft and, over time, impede the rotation of the shaft. This will cause a noticeable decrease in the performance of the watercraft. Similarly, other elongated objects could potentially be ingested by the watercraft propulsion system and could potentially foul the drive shaft. For example, a rope with a small diameter or a fishing line could enter the water passage and become wrapped around the rotating drive shaft, impeding operating performance.

[0009] Ideally, to prevent the ingestion of foreign matter by the propulsion unit, the watercraft should be fitted with a grate over the inlet to the water passage with small openings. Unfortunately, the smaller the openings provided in the grate, the more the grate interferes with watercraft performance. A balance, therefore, exists between the size of the openings in the grate and the output power of the watercraft. This means, necessarily, that the holes will be large enough to permit a certain amount of foreign matter to enter the water passage through the grate.

[0010] One solution to this problem in the prior art concerns a shaft guard that has been incorporated into jet boats manufactured by Bombardier Motor Corporation of America.

[0011] The shaft guard incorporated into prior art jet boats is illustrated in detail in FIG. 12. As illustrated, the prior art shaft guard 100 has a first end 102 and a second end 104. The first end of the shaft guard 102 attaches to the interior surface of the water tunnel of the watercraft by a number of finger-like structures 106. The finger-like structures 106 insert into a snap fitting within the water tunnel. The second end 104 of the shaft guard 100 connects to a number of finger-like elements (not shown) that extend from the pump housing structure 108 that defines the inlet opening to the impeller (not shown in FIG. 12). The drive shaft 110, which is operatively connected to the impeller, is disposed through the center of the shaft guard 100.

[0012] The prior art shaft guard 100 was specifically designed for use on a jet boat with an engine that generated a lower power output and torque than the engine preferred for use on the sport boat of the present invention. Accordingly, the shaft guard 100 was designed to withstand the smaller stresses and strains that were imposed upon it by the prior art jet propulsion system. Therefore, a problem was encountered immediately when the designers of the present invention considered the incorporation of that prior art shaft guard 100 into a modern sport boat with a more powerful jet propulsion system.

[0013] Specifically, the engine in a modern sport boat is considerably more powerful than the engine on prior art jet boats. As a result, the finger-like structures 106 on the prior art shaft guard 100 present two insurmountable problems to the incorporation of that shaft guard 100 onto a modern sport boat. First, the speed at which the water flows through the tunnel in a sport boat is considerably greater than the speed at which the water flows through the water passage on a prior art jet boat. At the higher speeds of the water in the water passage of a modern sport boat, the finger-like structures 106 introduce turbulent flow that is sufficiently strong to introduce cavitation into the water stream. Cavitation not only may damage the impeller and supporting structures but it also reduces the performance of the sport boat. Second, if a rope or other elongated foreign object were to become entangled in the impeller and not ingested by it, the elongated debris would eventually wrap around the shaft guard 100. Due to the considerable horsepower and torque generated by the engine in a modern sport boat, elongated debris wrapped around the shaft guard and caught in the impeller could exert sufficient force on the shaft guard 100 to cause it to break or to bend within the water passage. This would likely result in a reduction in performance of the vessel.

[0014] In view of the foregoing, a need has developed for a watercraft design where foreign material is prevented from becoming wrapped around the drive shaft for a modern sport boat (or a boat with a power output greater than that for jet boats in the prior art) but the performance of the watercraft is not hindered or limited because of such a design.

SUMMARY OF THE INVENTION

[0015] It is, therefore, an object of the present invention to provide a watercraft with a design where foreign matter is discouraged from wrapping around the drive shaft of the jet propulsion unit but also where watercraft performance, speed, and handling are not sacrificed.

[0016] One embodiment of the present invention provides a watercraft including a hull, an engine, an engine output shaft, a jet propulsion unit, and a shaft guard. The engine is mounted within the hull. The jet propulsion unit is associated with the hull and includes a housing, a drive shaft, and an impeller. The housing defines the water passage and is disposed partially within the tunnel. The drive shaft has one end rotationally connected to the engine output shaft and extends into the water passage and the tunnel. The engine output shaft and the drive shaft may or may not be oriented so that they are parallel to one another. The impeller is fixedly attached to the second end of the drive shaft. The shaft guard at least partially surrounds the drive shaft located within the jet propulsion unit and is mounted to the housing at one end allowing for free rotation of the drive shaft therein.

[0017] Another embodiment of the present invention provides a watercraft including a hull, an engine, a jet propulsion unit, and a shaft guard. The engine is mounted within the hull. The jet propulsion unit is associated with the hull and includes a housing, a drive shaft, and an impeller. The housing defines the water passage and is disposed partially within the tunnel. The drive shaft has one end rotationally coupled to the engine output shaft and extends through the water passage into the tunnel. The impeller is fixedly attached to the second end of the drive shaft. The shaft guard at least partially surrounds the drive shaft located within the jet propulsion unit. The shaft guard is mounted to the housing at one end and is attached to the drive shaft at the second end permitting the drive shaft to rotate therein.

[0018] The present invention also provides several methodologies for attaching the shaft guard to the watercraft so that it may be maintained in positional relationship to the drive shaft.

[0019] Other embodiments of the present invention will be made apparent in the description of the invention that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present invention. In the figures:

[0021]FIG. 1 is a cross-sectional side view of the watercraft of the present invention;

[0022]FIG. 2 is a cross-sectional view of the jet propulsion unit of the present invention;

[0023]FIG. 3A is an enlarged cross-sectional view of the jet propulsion unit and shaft guard of the present invention;

[0024]FIG. 3B is an enlarged section of the cross-section of FIG. 3A, taken within the region encircled by a dotted line in FIG. 3A;

[0025]FIG. 4 is an enlarged cross-sectional view of a portion of the shaft guard and housing of the jet provision unit of the present invention;

[0026]FIG. 5 is an alternative enlarged cross-sectional view of a portion of the shaft guard and housing of the jet propulsion unit of the present invention;

[0027]FIG. 6 is an enlarged cross-sectional view of a portion of still another alternative embodiment of the shaft guard and housing of the jet propulsion unit of the present invention;

[0028]FIG. 7 is a side view illustration of another embodiment of the shaft guard of the present invention;

[0029]FIG. 8 is an end view of the first end of the shaft guard illustrated in FIG. 7, the end view being taken at the end connected to the water passage;

[0030]FIG. 9 is an end view of the second end of the shaft guard illustrated in FIG. 7, the end view being taken at the end of the shaft guard closest to the impeller within the water passage;

[0031]FIG. 10 is an illustration of the attachment tab disposed at the first end of the shaft guard of the present invention;

[0032]FIG. 11 is a cross-sectional side view illustration of the shaft guard shown in FIG. 7, the view showing the bushing inserted into the second end thereof;

[0033]FIG. 12 is an exploded illustration of a conventional shaft guard as installed on a jet boat;

[0034]FIG. 13 is a side view of an alternative embodiment of the connection between the shaft guard and the watercraft;

[0035]FIG. 14 is a side view of still another alternative embodiment of the connection between the shaft guard and the watercraft;

[0036]FIG. 15 is a side view illustration of the shaft guard shown in FIG. 14, illustrating the steel spring tabs that for a part thereof; and

[0037]FIG. 16 is a side view of an exemplary embodiment of a pump assembly for the watercraft of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Throughout the description of the several embodiments of the present invention, reference will be made to various elements, the construction of which is readily known to those skilled in the art. Accordingly, an exhaustive description of each and every component is not provided, only a description of those elements required for an understanding of the present invention.

[0039]FIG. 1 is a cross-sectional view of the watercraft of the present invention. In the illustrated embodiment, the watercraft 10 is a jet boat that includes a hull 20 with a bow 21 and a stern 22. While jet boats are the preferred focus for the present invention, those of ordinary skill in the art would readily recognize that the present invention may be applied to any style boat. Since the deck and hull configuration is not critical to an understanding of the present invention, the details of the deck and hull are omitted from the figures.

[0040] In the illustrated embodiment, the watercraft 10 of the present invention is powered by an internal combustion engine 30. While the internal combustion engine 30 is shown in a position where the bulk of the engine 30 extends toward the bow 21 of the watercraft 10, other arrangements are also possible without departing from the scope of the present invention. In particular, the body of the engine 30 may extend toward the stem 22 of the watercraft 10, which provides for a more compact construction of the drive unit if the watercraft 10 than the one illustrated in FIG. 1. Alternatively, the watercraft 10 could be powered by an inboard engine of any type, equipped with a propeller.

[0041] As shown, the engine 30 is vertically mounted along the longitudinal axis of the hull 20 near the stem 22 of the watercraft 10. The vertical orientation of the engine 30 and its position near the stem (or rear) 22 of the watercraft 10 are not required to practice the present invention, however. It would be understood by those skilled in the art that the engine 30 could be mounted in any other suitable location or in any alternative orientation. For example, the engine 30 could be oriented so that it is nearly horizontal in the center of a watercraft 10, which is a typical arrangement for personal watercraft.

[0042] In the embodiment illustrated in FIG. 1, the engine 30 is operatively connected to a jet propulsion unit 40 by an engine output shaft 35. Normally, the engine output shaft 35 is integrally formed with and extends from the crankshaft (not shown) of the engine 30. However, as would be appreciated by those skilled in the art, the engine output shaft 35 could be mechanically connected to the crankshaft so that the output shaft 35 comprises two or more shafts connected together. In addition, the shafts could be connected through a gearbox or clutch arrangement, if desired for the particular design of the watercraft 10. In other words, a multiple shaft arrangement may be disposed between the engine 30 and the jet propulsion unit 40.

[0043]FIGS. 2 and 3 illustrate the engine 30 and jet propulsion unit 40 in progressively greater detail. As shown, the jet propulsion unit 40 comprises a housing 41 defining a water passage 42 therein. Although the housing 41 can be integrally manufactured as part of the hull (as illustrated in FIG. 1), the housing 41 may be manufactured as part of the pump assembly 31 (see FIG. 16), which is integrated into the hull 20 along with the engine 30 during construction of the watercraft 10. The water passage 42 is a curved structure extending from a point at the bottom of the hull 20 to a point above the bottom, at the rear of the hull 20. The water passage 42 is open at both ends.

[0044] The rear of the water passage 42 includes a tunnel 55, which is the portion of the water passage above the ride plate 56 that surrounds the impeller 44.

[0045] The forward end of the water passage 42 (which is the end at the bottom of the hull 20) acts as an entry (or inlet) to the water passage 42. The rearward end of the water passage 42 (which is at the rear of the watercraft 10) acts as the discharge outlet for the water passage 42.

[0046] At the forward end of the water passage 42, a grate 46 is mounted to the hull 20 of the watercraft 10 or mounted to the pump assembly 31 directly. As illustrated, the grate 46 has openings such that the openings allow for a sufficient amount of water to flow into the water passage 42, but the structure of the grate 46 also is substantial enough to prohibit most foreign matter from entering the water passage 42. Alternatively, the grate 46 may be a solid component with perforations or slots, or the grate 46 may be a wire mesh.

[0047] In the embodiment depicted, a drive shaft 43 is rotationally coupled to the engine output shaft 35 at the forward end of the drive shaft 43. The drive shaft 43 is oriented substantially horizontally and extends through the housing 41 and into the water passage 42. Alternatively, the drive shaft 43 may be oriented in any position, as long as it is rotationally coupled to the engine output shaft 35. In this embodiment, the drive shaft is disposed parallel to the longitudinal center line of the watercraft 10. Alternatively, the drive shaft 43 may be angled to any degree relative to the centerline of the watercraft 10 (i.e., toward the port or starboard sides), depending on design considerations known to those skilled in the art. Also, while the drive shaft 43 shown is disposed horizontally within the hull 20, those of ordinary skill in the art would readily appreciate that the drive shaft 43 may be angled above or below horizontal without departing from the scope of the present invention.

[0048] Additionally, while the drive shaft 43 is shown as a unitary shaft throughout the figures, those skilled in the art would readily appreciate that the drive shaft 43 could comprise two or more shafts operationally connected to and aligned with one another. For example, the drive shaft 43 could include two or more shafts mechanically connected (e.g., by a flange) to one another. Alternatively, the drive shaft 43 could be constructed from several shafts operatively connected to one another through a gearbox or clutch, if desired.

[0049] In one embodiment, as illustrated, the drive shaft 43 and the engine output shaft 35 are rotationally coupled such that the drive shaft 43 and the engine output shaft 35 are not substantially parallel. That is, an angle 60 greater than zero is formed between the longitudinal axis of the engine shaft 35 and the longitudinal axis of the drive shaft 43. As defined herein, the angle 60 formed between the longitudinal axis of the engine output shaft 35 and the longitudinal axis of the drive shaft 43 is, by definition, between about 5 degrees to about 175 degrees, no matter the configuration between the engine 30 and jet propulsion unit 40. Preferably, the angle 60 is between about 45 degrees to about 135 degrees. More preferably, the angle 60 is about 90 degrees. In the case of a personal watercraft, the preferred angle is about 180 degrees.

[0050] In the illustrated embodiment, the engine output shaft 35 and the drive shaft 43 are located in the plane that vertically bisects the hull 20 from the bow 21 to the stern 22. Alternatively, the engine output shaft 35 and the drive shaft 43 may not be disposed within the plane that bisects the hull 20 from the bow 21 to the stern 22. One of ordinary skill in the art would understand that the engine output shaft 35 and the drive shaft 43 can be oriented in any position within the hull 20 of the watercraft 10 suitable for propulsion of the watercraft 10 without departing from the scope of the present invention.

[0051] At the other end of the drive shaft 43 is the impeller 44. In this embodiment, the impeller 44 is fixedly attached to the rearward end of the drive shaft 43. Alternatively, the impeller 44 may be attached to the drive shaft 43 at some intermediate point along the drive shaft 43 other than at the end. The impeller 44 may be of any suitable design known to one skilled in the art. As illustrated in FIG. 3A, the impeller 44 is held in the water passage 42 by a stator 51. The stator 51 is a housing around the impeller that is connected to the walls of the water passage 42 by three or four vanes 53. Alternatively, the impeller 44 may be supported by a wear ring (not shown).

[0052] The shaft guard 45 of the watercraft 10 of the present invention is illustrated in FIGS. 3A and 3B. In the illustrated embodiment, the shaft guard 45 covers substantially the entire portion of the drive shaft 43 that is inside the water passage 42. The forward end of the shaft guard 45 is attached to the housing 41 and extends away from the housing towards the impeller 44, but does not cover, or interfere with, the operation of impeller 44. Embodiments illustrating this particular construction are set forth below and are illustrated in FIGS. 13-15 herein.

[0053] As illustrated in FIGS. 3A and 3B, the shaft guard 45 extends from the housing 41 to the point where the impeller 44 is connected to the drive shaft 43. While this embodiment is preferred, it should be noted that the shaft guard 45 may only extend to an intermediate point along the drive shaft 43 between the housing 41 and the impeller 44. Regardless of the extent to which the shaft guard 45 extends along the drive shaft 43, the shaft guard 45 should be positioned to discourage debris from becoming wrapped around the drive shaft 43.

[0054] It is preferred that the shaft guard 45 extend around the entirety of the drive shaft 43 because the shaft guard 45 acts as a buffer between the drive shaft 43 and the water being pumped through the water passage 42.

[0055] In prior art jet-propelled watercraft that do not include any shaft guard 45, the drive shaft 43 tends to impart rotation to the water being pumped through the water passage 42. As a result, when the watercraft is turned, the rotational momentum of the water in the water passage 42 can negate some of the momentum imparted to the water being circulated at the impeller 44. This can result in a slight (but noticeable) drop in output propulsion power for the vehicle.

[0056] Additionally, any rotational energy imparted by the drive shaft 43 to the water being pumped through the propulsion unit 40 is energy “lost” by the propulsion unit 40. Ideally, to maximize thrust, the energy imparted by the impeller 44 to the water would direct the water in a straight line from nozzle 48. Of course, the impeller 44 naturally imparts at least some rotational motion to the water in the water path 42. This motion is directed around the drive shaft 43 and not out of the nozzle 48. Accordingly, this energy is lost—the energy is not being utilized to propel the watercraft 10. The drive shaft 43 also can impart some rotational energy to the water in the water passage 42, contributing to the losses inherent in the jet propulsion unit 40. The addition of the shaft guard 45, especially if it covers the full length of the drive shaft 43 in the water passage 42, helps to minimize rotational losses because the shaft guard 45 acts as a barrier to prevent the drive shaft 43 from contributing to rotational energy losses.

[0057] If the shaft guard 45 extends from the housing 41 to the impeller 44, the entirety of the drive shaft is covered. This minimizes energy losses due to rotational energy being imparted to the water in the water passage 42. Of course, the drive shaft 43 need not be fully encased by the shaft guard 45, as would be appreciated by those skilled in the art.

[0058] The shaft guard 45 is attached to the housing 41 by an adhesive 47, as illustrated by FIG. 4. The adhesive may be of any type suitable for holding the shaft guard 45 in fixed relation to the drive shaft 43.

[0059] Alternatively, the shaft guard 45 may be affixed to the housing 41 through a suitable flange 49, as illustrated by FIG. 5. The flange 49 may be affixed both to the shaft guard 45 and to the housing 41 by a suitable adhesive. FIG. 6 shows a further embodiment where a flange 49′ is positioned on the interior of the shaft guard 45.

[0060] Alternatively, the connection may be made by any other suitable fastener such as the combination of nuts and bolts.

[0061] In the embodiment depicted in FIG. 3A, the shaft guard 45 completely surrounds the circumference of the drive shaft 43. In this regard, the shaft guard 45 is a tube that completely surrounds the circumference of the drive shaft 43. Alternatively, the shaft guard 45 can partially surround the circumference of the drive shaft 43 such that only the bottom half of the drive shaft 43 is covered, leaving the top exposed.

[0062] The shaft guard 45 also may have any cross-sectional shape, e.g., a circle, an ellipse, a triangle, a rectangle, an octagon, or the like, or any portion thereof. The shaft guard 45 shown throughout the figures has a cross-sectional shape of a circle. The shaft guard 45 can be perforated or slotted or be configured as a mesh or a cage. In the illustrated embodiment, the shaft guard 45 is solid (i.e., not perforated). In addition, the shaft guard 45 is preferably streamlined to minimize turbulence as the water flows around its exterior surface.

[0063] The shaft guard 45 can be formed from any material that will survive a salt water environment for a sustained period of time. Preferably, the shaft guard 45 is made from a plastic or a composite material (e.g., the material used to construct the housing 41). Alternatively, the shaft guard 45 is made from aluminum, stainless steel, or the like.

[0064] In another embodiment, illustrated by FIGS. 3A and 3B, the rearward end of the shaft guard 45 is attached to the drive shaft 43 by a supporting member 50 such that the drive shaft 43 is free to rotate. In this embodiment, the supporting member 50 is a bushing, which may or may not be lubricated. The bushing 50 permits free rotation of the drive shaft 43 while also maintaining the orientation of the drive shaft 43 roughly in the center of the guard shaft 45. Alternatively, the supporting member 50 may be a bearing such as a ball bearing, which may be open or closed, lubricated or not.

[0065] A further embodiment of the present invention is illustrated in FIGS. 7-11. As shown, the shaft guard 72 is essentially a cylindrical structure with an angled end 74 and a end 76 that has been cut essentially perpendicularly to the longitudinal axis 78 of the shaft guard 72. The angled end 74 is shaped to mate with the housing 41 of the water passage 42 in the same manner that shaft guard 45 mates with the housing 41 as illustrated in FIGS. 3A, 4, 5, and 6. As illustrated in FIG. 8, the angled end 74 appears elliptical in shape when viewed end-on. Since the other end 76 is cut substantially perpendicularly to the longitudinal axis 78 of the shaft guard 72, that end 76 has a circular cross-section when viewed end-on, as illustrated in FIG. 9.

[0066] The shaft guard 72 is constructed from a material that is resistant to corrosion in a salt water environment. Specifically, the shaft guard 72 is constructed from stainless steel, aluminum or a material containing aluminum. More specifically, the shaft guard 72 is constructed of 304 stainless tubing. Alternatively, the shaft guard 72 may be constructed from a plastic or composite material so long as the material can withstand: (1) the forces generated within the water passage 42 during operation of the watercraft 10 and (2) the forces exerted by an elongated object that becomes entangled in the impeller 44 and wraps around the shaft guard 72.

[0067] To attach the angled end 74 of the shaft guard 72 to the housing 41 within the water passage 42, a pair of eyelets 80 are affixed thereto or are fashioned as a part thereof. Fasteners, such as bolts (not shown) are inserted through the eyelets 80 to attach the shaft guard 72 to the housing 41. The eyelets 80 are made from a corrosion-resistant material, such as stainless steel, aluminum or a material containing aluminum. Specifically, the eyelets 80 are made from 304 stainless steel. Alternatively, the eyelets 80 could be fashioned from a plastic or composite material so long as the material can withstand the dynamic forces within the water passage 42. In the embodiment shown, the shaft guard 72 and eyelets 80 are made of 304 stainless steel. When made of steel, the eyelets 80 are welded to the angled end 74 of the shaft guard 72. If manufactured as a part of the shaft guard 72, the eyelets 80 understandably will be made from the same material as the shaft guard 72.

[0068] To provide support for the shaft guard at the transversely cut end 76, a support member 82 is provided. The support member 82 preferably is a bushing that is press-fitted into the end 76. The bushing 82 preferably is constructed from bronze, stock SAE 841. As would be understood from the FIG. 11, the interior surface of the bushing 82 engages the exterior surface of the drive shaft 43. While a bronze bushing is preferred for the shaft guard 72 of the present invention, alternatively, a bearing could be used.

[0069]FIG. 13 illustrates a side view of another alternative for connecting the shaft guard 45 to the hull 41. Here, the shaft guard 45 is welded to a flat washer or collar 84. The collar 84, in turn, is welded to two keys 86, 88 that interlock with the through-hull fitting 90. The through-hull fitting 90 is a member that extends through the hull to permit the drive shaft 43 to be operatively connected to the engine 30.

[0070] Since the through-hull fitting 90 is connected to the hull 41 so that the through-hull fitting 90 cannot rotate, the keys 86, 88 that interlock with the through-hull fitting 90 prevent the shaft guard 45 from rotating. To permit the drive shaft 43 to rotate with respect to the shaft guard 45, two support members 82, preferably bushings, are disposed within the shaft guard 45 at forward and rearward ends thereof. While a bronze bushing is preferred for the support member 82 of the present invention, alternatively, a bearing could be used.

[0071] To prevent the shaft guard 45 from moving axially along the drive shaft 43, a compression spring 92 is positioned between the collar 84 and a carbon seal 94. The compression spring 92 biases the shaft guard 45 in a forward direction. In addition, a C-clip also assists in maintaining the shaft guard 45 in its forward direction by preventing the carbon seal 94 from slipping rearwardly along the drive shaft 43.

[0072]FIG. 14 is a side view of yet another embodiment of a connection between the shaft guard 45 and the through-hull fitting 90. Here, instead of a pair of keys 86, 88 that hold the shaft guard 45 in a fixed relationship to the hull 41, three bent spring steel forms 96 are used. To simplify illustration of this connection, only two bent steel spring forms 96 are illustrated in FIGS. 14 and 15. As would be appreciated by those skilled in the art, while this embodiment contemplates reliance on three bent steel spring forms, any number greater than one is all that is required to hold the shaft guard 45 in a fixed relationship to the through-hull fitting 90.

[0073] As illustrated in FIG. 14, the bent steel spring forms 96 have a forward end 97 and a rearward end 98. The forward ends 97 engage small holes 99 in the through-hull fitting 90. The rearward ends 98 of the bent steel spring forms 98 engage notches (or other similar structure(s) in the rear end of the through-hull fitting 90 to maintain the shaft guard 45 in a fixed positional relationship thereto.

[0074]FIG. 15 illustrates the shaft guard 45 and bent steel spring forms 96 as they would appear when disconnected from the through-hull fitting 90. As illustrated here and also in FIG. 14, the bushing 82 may be bronze. However, as would be appreciated by those skilled in the art, any alternative support, such as a bearing, could be substituted therefor without deviating from the scope of the present invention.

[0075] From the invention just described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims. 

What is claimed is:
 1. A watercraft comprising: a hull; an engine mounted within the hull; an engine output shaft operatively connected to the engine; a jet propulsion unit associated with the hull, wherein the jet propulsion unit comprises a housing defining a water passage; a drive shaft with a first end and a second end, wherein the drive shaft first end is rotationally coupled with the engine output shaft and the second end extends into the water passage; an impeller operatively attached to the drive shaft second end and disposed within the water passage; and a shaft guard with a first end and a second end, the shaft guard at least partially surrounding the drive shaft second end, the shaft guard first end mounted to the housing, the shaft guard permitting free rotation of the drive shaft therein.
 2. The watercraft according to claim 1, wherein the engine output shaft and drive shaft are substantially parallel.
 3. The watercraft according to claim 1, wherein the engine output shaft and drive shaft are not substantially parallel.
 4. The watercraft according to claim 1, wherein the shaft guard fully surrounds the drive shaft second end.
 5. The watercraft according to claim 4, wherein the shaft guard is a tube.
 6. The watercraft according to claim 5, wherein the shaft guard is circular in cross-section.
 7. The watercraft according to claim 5, wherein the shaft guard is streamlined in cross-section.
 8. The watercraft according to claim 6, wherein the shaft guard is made from stainless steel.
 9. The watercraft according to claim 1, wherein the first end of the shaft guard comprises at least one eyelet affixed thereto, adapted to receive a fastener therethrough.
 10. The watercraft according to claim 1, wherein the at least one eyelet comprises two eyelets that are welded to the first end of the shaft guard.
 11. The watercraft according to claim 1, further comprising: a through-hull fitting mounted to the housing; a collar attached to the first end of the shaft guard; and at least two keys affixed to the collar in registry with the through-hull fitting, wherein the keys maintain the collar and shaft guard in positional relationship with the through-hull fitting.
 12. The watercraft of claim 11, further comprising: a C-clamp attached to the drive shaft; a carbon seal positioned around the drive shaft adjacent to the C-clamp; a compression spring disposed between the carbon seal and the collar, wherein the compression spring biases the shaft guard away from the carbon seal.
 13. The watercraft according to claim 1, further comprising: a through-hull fitting mounted to the housing, the through-hull fitting defining at least two openings therein; and at least two bent steel spring forms connected to the first end of the shaft guard, wherein the bent steel spring forms register with the openings in the through-hull fitting to maintain the shaft guard in positional relationship with the through-hull fitting.
 14. A watercraft comprising: a hull; an engine mounted within the hull; an engine output shaft operatively connected to the engine; a jet propulsion unit associated with the hull, wherein the jet propulsion unit comprises a housing defining a water passage; a drive shaft with a first end and a second end, wherein the drive shaft first end is rotationally coupled with the engine output shaft and the second end extends into the water passage; an impeller operatively attached to the drive shaft second end and disposed within the water passage; and a shaft guard with a first end and a second end, the shaft guard at least partially surrounding the drive shaft second end, the shaft guard second end comprising a support member that slidingly engages one of the impeller or the drive shaft second end, allowing for free rotation of the drive shaft.
 15. The watercraft according to claim 14, wherein the support member is a bushing.
 16. The watercraft according to claim 15, wherein the bushing is made of bronze.
 17. The watercraft according to claim 14, wherein the engine output shaft and drive shaft are substantially parallel.
 18. The watercraft according to claim 14, wherein the engine output shaft and drive shaft are not substantially parallel.
 19. The watercraft according to claim 14, wherein the shaft guard fully surrounds the drive shaft second end.
 20. The watercraft according to claim 19, wherein the shaft guard is a tube.
 21. The watercraft according to claim 20, wherein the shaft guard is circular in cross-section.
 22. The watercraft according to claim 20, wherein the shaft guard is streamlined in cross-section.
 23. The watercraft according to claim 22, wherein the shaft guard is made from stainless steel.
 24. A watercraft comprising: a hull; an engine mounted within the hull; an engine output shaft operatively connected to the engine; a jet propulsion unit associated with the hull, wherein the jet propulsion unit comprises a housing defining a water passage; a drive shaft with a first end and a second end, wherein the drive shaft first end is rotationally coupled with the engine output shaft and the second end extends into the water passage; an impeller operatively attached to the drive shaft second end and disposed within the water passage; and a shaft guard with a first end and a second end, the shaft guard at least partially surrounding the drive shaft second end, the shaft guard first end mounted to the housing, the shaft guard second end comprising a support member that slidingly engages one of the impeller or the drive shaft second end, wherein the shaft guard allows free rotation of the drive shaft therein.
 25. The watercraft according to claim 24, wherein the support member is a bushing.
 26. The watercraft according to claim 25, wherein the bushing is made of bronze.
 27. The watercraft according to claim 24, wherein the engine output shaft and drive shaft are substantially parallel.
 28. The watercraft according to claim 24, wherein the engine output shaft and drive shaft are not substantially parallel.
 29. The watercraft according to claim 24, wherein the shaft guard fully surrounds the drive shaft second end.
 30. The watercraft according to claim 29, wherein the shaft guard is a tube.
 31. The watercraft according to claim 30, wherein the shaft guard is circular in cross-section.
 32. The watercraft according to claim 30, wherein the shaft guard is streamlined in cross-section.
 33. The watercraft according to claim 31, wherein the shaft guard is made from stainless steel.
 34. The watercraft according to claim 24, wherein the first end of the shaft guard comprises at least one eyelet, adapted to receive a fastener therethrough, permitting attachment of the shaft guard to the housing.
 35. The watercraft according to claim 34, wherein the at least one eyelet comprises two eyelets that are welded to the first end of the shaft guard.
 36. The watercraft according to claim 24, further comprising: a through-hull fitting mounted to the housing; a collar attached to the first end of the first end of the shaft guard; and at least two keys affixed to the collar in registry with the through-hull fitting, wherein the keys maintain the collar and shaft guard in positional relationship with the through-hull fitting.
 37. The watercraft according to claim 24, further comprising: a through-hull fitting mounted to the housing, the through-hull fitting defining at least two openings therein; and at least two bent steel spring forms connected to the first end of the shaft guard, wherein the bent steel spring forms register with the openings in the through-hull fitting to maintain the shaft guard in positional relationship with the through-hull fitting.
 38. A shaft guard comprising: a first end having at least one tab affixed thereto, the tab having a hole adapted to receive a fastener therethrough for mounting to the housing of a jet pump assembly; a second end, adapted to at least partially surround a drive shaft of a jet pump assembly; and a support member, disposed within the second end and adapted to slidingly engage one of an impeller or drive shaft of a jet pump assembly, wherein the shaft guard allows free rotation of the drive shaft therein.
 39. A shaft guard comprising: a hollow tube with a first end; a collar affixed to the first end; and at least two keys affixed to the collar, wherein the keys are adapted to register with a through-hull fitting, wherein the keys maintain the collar and hollow tube in positional relationship with the through-hull fitting.
 40. A shaft guard comprising: a hollow tube with a first end; at least two bent steel spring forms connected to the first end; wherein the bent steel spring forms are adapted to register with one of either the holes and notches in a through-hull fitting to maintain the hollow tube in positional relationship with the through-hull fitting. 